Allostatic Load Mediates Associations Between Race and Ethnicity and Hypertensive Disorders of Pregnancy.

OBJECTIVE To evaluate whether chronic stress exposure, measured by allostatic load (a biological measure of chronic stress embodiment, including stressors exacerbated by structural inequities [eg, structural racism]) and patient-reported perceived stress in the first trimester of pregnancy, mediates the association between self-identified race and ethnicity and hypertensive disorders of pregnancy (HDP). METHODS This was a secondary analysis of data from nuMoM2b (Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be), a large prospective cohort study. We evaluated self-identified race and ethnicity as an independent variable (non-Hispanic Black, Hispanic, Asian, non-Hispanic White), and our outcome of interest was HDP (ie, gestational hypertension, preeclampsia or eclampsia). Allostatic load was operationalized with regression- and count-based approaches. Perceived stress was collected with the Cohen perceived stress scale. We investigated allostatic load and perceived stress and used causal mediation analyses with a counterfactual approach to evaluate whether they mediated the association between self-identified race and ethnicity and HDP, adjusting for age and tobacco use. Mediation analyses were conducted for each minoritized racial and ethnic group compared with non-Hispanic White participants. RESULTS The sample included 645 participants who developed HDP and 2,438 participants without HDP or other adverse pregnancy outcome. Allostatic load and perceived stress varied by race and ethnicity; HDP varied by allostatic load but not perceived stress. Allostatic load was a partial mediator exclusively in the comparison of non-Hispanic Black and non-Hispanic White participants (0.027, 95% CI, 0.013-0.040, P<.001; 28.9%). Perceived stress was not a significant mediator. CONCLUSION First-trimester allostatic load mediated the association between self-identified race and ethnicity and HDP for non-Hispanic Black and non-Hispanic White participants. This mediation effect was not observed in other racial and ethnic comparisons. These results demonstrate a physiologic pathway through which racism may contribute to adverse pregnancy outcomes and suggest that interventions targeting allostatic load reduction could help address racial and ethnic disparities in HDP.